Process of esterification



May8,1923. -1,454,463

A. A. BACKHAUS I PROCESS OF ESTERIF'ICATION Filed Sept. 20. 1919 2 Sheets-Sheet 1.

a mwntoz .May 8, 1923 1,454,463

. A. A. BACKHAUS PROCESS OF ESTERIFICATION Filed Sept.- 20, 1919 2 Sheets-Sheet 2 I "In ARTHUR A. BAcxHAus, or BALTIMORE, MARY ALCOHOL 00., A CORPORATION OF WEST VIRGINIA.

rnocnssor EST a ICATION.

Application filed September 20, 1919. Serial Ho. 825,107.

To all whom it may concern: 4

Be it known that I, ARTHUR A. BA K- HAUS, a citizen of the United States, residing at Baltimore, State of Maryland, have invented a certain new and useful Improvement in Processes of Esterification, of which the following is a specification.

My invention relates particularly to a process of producing esters having a high grade of purity by providing an effective method of esterification, but it relates especially to the production of ethyl acetate in this manner, which is substantially free from alcohol. I I

The" object of my invention is to pro-' vide a process of esterification'by means of which the highest yields of esters may be obtained and the object of my invention is furthermore to obtain esters in this way having a high degree of purity especially ethyl acetate of substantially 100% strength.

Another object of my invention is to provide such a process in which the organic acid and alcohol are subjected to the action of a catalyst for the maximum period of time during which the esterifi cation will take place, inasmuch as I have discovered that there is a fixed period of time during which the treatment must continue in order to obtain the maximum esterification irrespective of the percentage of the organic acid present.

Further objects of my invention will ap-' pear from-the detailed description thereof.

contained herein-after. y

While my'invention is capable of embodiment in many difierent forms, for the purpose of illustration I" shall describe only certain forms-of the same hereinafter, and while it is capable of being carried out in connection with many difiere'nt types of apparatus, I have shown only-one type of apparatus for use in connection therewith in the accompanying drawing,-in which;

The figure 1s a' diagrammatic representation of an apparatus which may be used in connection with my invention.- I

While my invention is capable of being carried out in connection with the manufacture of diflerent esters, and with the use of different starting materials, I shall by way of example describb the invention as applied to the manufacture of eth'l acetate from alcohol and vinegar with t e aid of sulphuric acid as a catalytic.

flow continuously by means of a valvedpipe In the drawing, I have shown two mixing tanks 1 and 2 which are designed to be used alternately, the; construction of which is exactly the same in the two tanks. v

The tank 1 is provided with three inlet pipes 3, 4 and 5 containing sulphuric acid, alcohol, and vinegar respectively. .These three materials are preferably fed into the tank 1 in about-the proportion'of .33 parts by weight of sulphuric acid having a strength of 50 to 66 B., to 10 parts by weight of vinegar havin a strength of 8% acetic a'cld, and part y weight of ethyl alcohol having a strength of95%. These materials are mixed in the tank 1 by means of an agitator .6 driven from any suitable source of power. The mixed materials are 'fed out of the tank l into a valved pipe 7 from which they are. discharged by a pump 8 through a pipe 9 into a supply tank 10.

The mixing tank 2 is also connected to the pipe 7 by means of a valved'branch pi e. 11, and it will be understood that in t e operation otthe apparatus the two mixing tanks land 2 will .be operated alternately. In-the present embodiment the pump 8 supplies these mixed materials to the supply tank 10 continuously, and therefrom they 12 through a combined dephlegmator and preheater 13, provided with tube sheets 14 and 15 and interposed tubes 16, through which these mixed materials are passed in order to be heated by heated vapors admitted between. the tube sheets 14 and 15 by an inlet pipe 17, the condensate being discharged by a pipe 18. From the preheater 13 the preheated materials are ledthrough a trapped'valved pipe 19 to the side of an esterification column '20 {maintained at a temperature of approximately 80 (3., at the top thereof. Heating steam passes into the column 20 through a perforated pipe 21 10- the bodies of liquid carried by thepans 22. In order tov accomplish this, as shown-in the drawings, there are located between the adjacent pans a series of overflow tubes 24 which are so located as to maintain large cated in the bottom thereof, and is thus I cause the ascending vapors to pass through bodies of liquid in the pans 2'3 and shallow the action of the catalyst in the column 20 for a length of time in any given instance in which the maximum degree of esterification obtainable will have been reached. This length of time is dependent upon the percentage of alcohol present. If there is only 20% of alcohol present the time required is one half hour, but it 60% of alcohol is present the time necessary will be one and one half hours. llt the storage pans 23 were not provided in the column 20 the maximum esterification obtainable would not be secured as the alcohol and acetic acid would not be subjected in any one given instance in the column 20 to the action of the catalyst for this length of time. From the bottom of the column 20, the slop containing sulphuric acid is preferably continuously discharged by a pipe 25 leading to an overflow bottle 26 having a vapor outlet pipe 27 leading back to the column 20 and a liquid discharge pipe 28 passing out from the bottom of the bottle 26. In the side of the column 20, there is alsoa further trapped inlet pipe 29 for feeding into the same alcohol havin a strength of 7090%, which is supplied From a portion of the apparatus to be hereinafter described.

Through the action of the catalyst, ethyl acetate is ormedinthe column, and continually passes out of the top of the same admixed with alcohol andsteam by means of the pipe 17 which is shown connected to the' dephlegmator and preheater 13. The

lower portion of the'vapor space in the dephlegmator and'preheater is connected by the pipe 18 to the upper portion of the column 20, so as to convey back into the same the first distillate in order to keep the pans sealed in the column. From this point the vapors pass from the dephleg'mator and preheater by a pipe 30 to a warm condenser 31 having two tube sheets 32'and 33 connected with a series of tubes 34, and the temperature of which is maintained at 60- "C., by a current of water passing into the 'same through inlet and outlet pipes 35 and 36. From this point the condensed liquid which comprises approximately 20% by weight of ethyl acetate, 60% by weight of alcohol, and 20% by weight of water passes out of the condenser by means of a pipe 37 to a bottle 38 having a valved trapped liquid outlet pipe 39 and a vapor outlet pipe 40 which latter leads to a cold condenser 41 having tube sheets 42 and 43 provided with a series of interposed tubes 44 menses .wardly in the apparatus back to the pipe 18,so as to allow the same to be discharged in the column 20. This pipe 51 has an upwardly bent portion 52, so that only such excess will pass through the pipe 51. The pipe 39 conveys the mixed ethyl acetate, alcohol, and water, into a separating column 53, the interior of which is constructed the same as in the case of the column 20, except that in this instance the storage pans 23,are omitted and only pans like the pans 22 are present and, furthermore, there is a steam heater 54 comprised of tube sheets 55 and 56 carrying a plurality of tubes 57. The upper portion of this column is maintained at a temperature of substantially 70 C. in the side of the column 53, there are additional trapped liquid inlet pipes 58 and 59 leading from parts of the apparatus to be hereinafter described, and at the bottom of the column 53 there is an outlet pipe 60 leading to an overflow bottle 61 connected by a vapor outlet pipe 62 to the column 53, and connected at its lower end to the pipe 29. The vapors which pass out of the top of the column 53 are comprised of a mixture of ethyl acetate, alcohol, and Water, the principal constituent of which is-ethyl acetate. These Vapors are conveyed by a pipe 63 to a dephlegmator 64 having tube sheets 65 and 66 carrying tubes 67 and provided with a trapped liquid return pipe 68 leading back to the top of the'column 53 in order to keep the pans therein sealed with liquid. The dephlegmator 64 is cooled by a current of cooling Water supplied with the aid of inlet and outlet pipes 69 and 70. From this dephlegmator 64 the uncondensed vapors pass by a pipe 71 to a condenser 72 having tribe sheets 73 and 74 carryingtubes 75 and cooied by a current of water supplied with the aid of inlet and outlet pipes 76 and 77. The condensate which comprises a constant boiling mixture of ethyl acetate, alcohol, and. water, contains approximately 83% of ethyl acetate, 9% of alcohol, and 8% of water,

and is conveyed out of the condenser 72 by the pipe 58 into the column 53.

menace connected in advance of said measuring receptacle 84 by means of a valved pipe 85 to the pipe 58, so that the liquid in the pipe '58 may, if desired, be also fed to the measuring receptacle 84 instead of bein led by when the liquid in the pi e 58 contains at least/80%- ester, it will be ed through the pipe 85 into the pipe 81, but if the percentage of the ester is lower, it will be fed instead by the pipe 58 back into the column 53. The measuring receptacle 84 has attached to the inlet pipe 81 therein a container 80 which discharges the liquid laterally near the inner periphery of the receptacle 84, and around the inlet pipe 81 there is located an outlet pipe 87 having a slot 88 with a scale 89 at the side thereof to indicate by the hei ht of the level ofthe liquid in the receptac e 84 the speed of outflow of the liquid. The pipe 87 con veys this constant boiling mixture of ethyl acetate, alcohol, and water, to a mixing coil 90 which is supplied with water by means of a pipe 91 leading from a measuring receptacle 92 constructed in the same manner as the measuring receptacle 84, and which is continuously supplied with water by means of a valved pipe 93. From the mixing coil 90 these liquids pass into a separating chamber 94 where the liquid separates into a lower water layer 95 containing small percentages of ethyl acetate and alcohol, and an upper layer 96 containin approximately 94% of ethyl acetate, 4% 0 water, and 2% of alcohol. The lower layer containing the small percentage of ethyl acetate passes out of the separating chamber '94 by a vented overflow pipe 91 to the pipe 59, and thence back to the column 53. The upper layer of liquid 96 containing a higher percentage of ester flows out of the chamber 94 by a trapped pipe 98 into the side of a drying column 99; This column 99 is constructed on the interior thereof in the same manner as the column 53. The lower portion of'the column 99 is maintained at a temperature of substantially The vapors passing out of the top of the column 99 are conveyed by a pipe 100 to a dephlegmator 101 having tube sheets 102 and 103,carrying' a plurality of tubes 104, and arranged to return the liquid therefrom by a trapped pipe 105 to the upper end of the column 99 in order to seal the pans therein. Said dephlegmator 101 is cooled in the usual manner by means of a current of water supplied with'the aid of inlet and outlet pipes l06 and 107. The unc'ondensed vapors pass out of the dephleg- -mator 101 by a pipe 108 to a condenser 109 having tube sheets 110 and 111 provided with tubes 112 and cooled by a current of water with the aid of inlet and outlet pipes 113 and '114. The condensate which will ordinarily comprise constant boiling mixtures of ethyl acetate, alcohol, and water,

- pipe 118 is connected by a valved pipe 119 to the pipe 105, so that when desired the liquid may be returned to the column 99 so as to avoid returning the liquid to the column 53 when the latter-or some part asso-- ciated therewith is to be thrown out of operation temporarily. Ordinarily, howeve'rythis pipe 119 will be closed and the liquid will be fed from the pipe 118 to the pipe 58, and thence either into the measurmg receptacle 84 or the column 53 according to the composition of the liquid as above pointed out. From the bottom of the column 99 ethyl acetate having a strength of 95 to 100% passes out by a pipe 120 to an overflow bottle 121 having a vapor outlet pipe 122 leading back to the column 99 and an outlet pipe 123 leading out of the bottom of the bottle 121. This pipe 123 conveys the ethyl acetate to a cooling coil 124 located in a cooler 125 cooled by a current of water supplied with the .aid of. inlet and outlet pipes 126 and 127. The cooled ethyl acetate passes away from the cooler 125 by means .of a trapped pipe 128, and is collected in a 1n starting filled with alcohol, then the sulphuric acid, alcohol, and vinegar are mixed in the proper proportions hereinabove referred to in the two tanks 1 and 2 alternately, and that from these tanks the mixed materials are conveyed continuously to the supply tank 10 from which they are continuously conveyed through the preheater 13 to the esterificationicolumn 20, from the bottom of which the slop containing sulphuric acid is continuously discharged, while the vapors of ethly acetate, alcohol, 1 and water pass out of the top of the same to the preheater13 which acts also as the dephlegmator, to return to the column 20 the first condensate. As previously pointed out, the action of the esterification column 20 is such as to' produce the maximum amount of esterification obtainable with the materials present inasmuch as the latter are subjected at any one point in the column 20 to the action of the catalyst for a sufficient length of time to produce a maximum yieldof the ester at this point, that is to say, ethyl acetate. Furthermore, the degree of esterificationobtainable at any given point in the column 20 will depend upon the percentage of the alcohol in the materials present as above pointed out and in general the percentage of the organic acid that will be transformed into the ester at any given point in the column 20 will be approximately the same percent as the percentage of the alcohol contained in the materials present. From the dephlegmator 13 the vapors pass into the hot condenser 31 and finally the cold condenser 41, so as to condense the vapors to a liquid with the minimum loss of heat, and thus obtain a mixture of ethyl acetate, alcohol and water in the form of a liquidprior to supplying the same to the separating column 53. llt is highly desirable to condense these vapors to a liquid at this point, as, otherwise, owing to the low latent heat of vaporization of the ethyl acetate present compared with the high latent heat of vaporization of the alcohol present, if these materials were fed into the column 53 in uncondensed form, the ethyl acetate in the column would be vaporized to a disadvantageous degree because of the large amountof heat present. In the column 53 the ester is separated from the alcohol, the alcohol being fed back into the esterification column while the ester and admixed remaining alcohol and water are obtained in the form of a constant boiling mixture which is thereafter intermingled with water in the coil 90, so as to form the two layers of liquid containing high and low percentages of ethyl acetate respectively in the chamber 94. The layer containing the lower percentage of ethyl acetate is fed back into.

the separating column 53 while the layer containing the higherpercentage of ethyl acetate is conveyedinto the drying or rectifying column 99 where the excess of the ester over the constant-boiling mixture of ethyl acetate, alcohol, and water is drawn off as a residue at the bottom, passed through the cooler 125, and received in the storage receptacle 129 the constant boiling mixture being returned from the top of the column 99 either to the measuring receptacle 84 or thecolumn 53. In this way, it is possible to obtain continuously ethyl acetate having a strength of 95 to 100% according to the operation of the apparatus.

It will be understood that other acids and other alcohols may be used instead of the acetic acid or vinegar and the ethyl alcohol, as for example butyric acid and methyl alcohol and that instead of the sulphuric acid another catalyst may be used, as for example hydrochloric acid or some other organic acid, such as' formic acid. a

While I have described my invention.

above in detail, I wish itto be understood that many changes may be made therein without departing from the spirit thereof.

I claim: 1. The prpcess which comprises esterifying an organic acid and an alcohol with the aid of a catalyst and removing some ofthe ester formed when the maximum esterificaesa-sea tion has been obtained, the reaction mixture being subjected to the passage of a heated current of vapors in alternating bodies of the same while the remaining bodies of the reaction mixture are maintained in storage.

'2. The process which comprises continuously esterifying an organic.acid and an alcohol with the aid of a catalyst and continuously removing some of the ester formed when the maximum esterification has been obtained, the IGZlCtlOH'llllXtlllQ being subject ed to the passage of a heated current of vapors in alternating bodies of the same while the remaining bodies of the reaction mixture are maintained in storage.

3. The process which comprises continuously esterifying an organic acid and an alcohol with the aid of a catalyst and continuously removing some of the ester formed when the maximum esterification has been obtained while continually feeding to the reaction mixture fresh quantities of the catalyst of the alcohol and the organic acid, the reaction mixture being subjected to the passage of a heated current of vapors in alternating bodies of the aime while the remaining bodies of the reaction mixture are maintained in storage.

4c. The process which comprises esterifying acetic acid and alcohol with the aid of a catalyst and removing some of the ester formed when the maximum esterification has been obtained,'the reaction mixture being subjected to the passage of a heated current of vapors in-alternating bodies of the same while the remaining bodies of the reaction mixture are maintained in storage.

5. The process which comprises continuously esterifying acetic acid and alcohol with the aid of a catalyst and continuously removing some of the ester formed when the maximum esterification has been obtained, the reaction mixture being subjected to the passage of a heated current of vapors in alternating bodies of the same while the remaining bodies of the reaction mixture are maintained in storage.

6. The process which comprises continuously esterifying acetic acid and alcohol with the aid of a catalyst and continuously removing some of the ester formed when the p maximum esterification has been obtained?-:

bodies of thereaction mixture are main-v tained in storage;

' 7. The process of making esters comprising introducing a mixture of alcohol, acid and catalyst into a column provided with alternating storage cups and gas and liquid contact cups, heating the column to assist 3130 esterification to subject the bodies oftion of 'the distilled liquids into a heated' separating column and distilling off there froma constant boiling mixture of alcohol, water and ester.

8. The rocess of making'esters comprising intro ucing a mixture of alcohol, acid and catalyst into a column provided with alternating storage cups and gas and liquid contact cups, heating the column to assist esterification and to subjectthe bodies of liquid in the cups to the heated vapors roduced, distilling oil the ester forme at substantially the rate at which it is formed in the said column,. introducing a portion of the distilled liquids into a heated separating column and distilling ofl therefrom a constant boiling mixture of alcohol, water and ester, and separating the ester from aqueous liquid'and distilling the ester to separate it from its constant boiling mixture with alcohol and water.

9. The process of making ethyl acetate comprising introducing a mixture of ethyl alcohol, acetic acid and sulphuric acid cata v lyst into a column provided with alternating storage cups and gas and liquid contact cups, heatlng the column to assist the esterification and to subject the bodies of liquid in thecups to the vapors produced and to maintain its top near 80 C. to distill ofi' the ethyl acetate at substantially the rate at which it is formed in the column, and condensing the ethyl acetate distillate and. separating it from the alcoholic liquor in a plate distilling column.

10. The process of making ethyl acetate com 'rising introducing a mixture of ethyl alco ol, acetic acid and sulphuric acid catalyst into a column'provided with alternating storage cups and gas and liquid contact cups, heating the column to assist the esterification and to subject the bodies of liquid in the cups to the vapors oduced and to main-' tain its top near 80 to distill ofi' the ethyl acetate at substantially the rate at which it is formed in the column, and condensing the ethyl acetate distillate y from the alcoholic liquor in a plate distilling column whose top is maintained at about C. whereby a constant boiling mixture of ester, alcohol and water is produced.

11. The process of making ethyl acetate comprising introducing a mixture of ethyl alco ol, acetic acid and sulphuric acid catalyst into a column provided with alternating off the ester forme at fi and separating it storage cups and gas and liquid contact cups, heating the column to assist-the este'ri-' cation and to subject the bodies of liquid in the cups to the vapors reduced and to maintain its top near to distill off the ethyl acetate at substantially the rate at. condensing which it is formed in the column, the ethyl acetate distillate and separating it fromthe alcoholic liquor in a plate distilling,

column, and further concentrating the liquid a constant boiling mixture of ester, alcohol and. water.

acid, and catalyst into a column provide with alternating storage cups and gas and liquid contact cups, heating the column to assist esterification and to subject the bodies of liquid in the cups to the heated vapors produced,'and distilling off the ester formed at substantially the rate at which it is formed in the said column.

13. The process of making ethyl, acetate comprising introducing a mixture of ethyl alcohol, acetic acid and an acid catalyst ,into acolumn provided with valternating storage cups and gas and liquid contact cups, heating the column to assist esterification and to subject the bodies of liquid in the cups to the heated vapors produced, and heating the column to maintain its top at about 80 C. to distill oif the ethyl acetate at substantially the rate it is distilled in the column.

14;. The process which comprises continu- 70 containing the ester distilling therefrom f ously esterifying an organic acid 'and an alcohol with the aid of a catalyst, continuously removing some of the ,ester formed when the maximum esterification has been obtained, and further esterifying the residue while continuously feedin to the reaction mixture fresh terials.

quantities o the reacting ma- 15. The processwhich comprises continu lyst, the reaction being subjected to the pas reacting materials.

. sage of a current of vapors evolved fromthe In testimony that I claim-the "foregoing, I r

have hereunto set my hand this 3rd day September, 1919. "'r A. BACAUS.

ously esterifying an organic acid and an al- 

